1. Field of the Invention
The present invention relates to the processing of digital images and, more particularly, to a method of obtaining a depth map from a digital image of a three-dimensional scene.
2. Description of the Related Art
Many applications of computer-assisted graphics call for knowledge of the depth map of a digital image, i.e. the distribution of the relative depths of the image points (pixels). The relative depths of a pixel is understood as the distance of the point of the three-dimensional scene represented by the pixel from a reference plane that, as a general rule, coincides with the plane of the image. The depth map is constituted by a gray-scale image in which each pixel is assigned a value according to its depth. It is usually assumed that the higher the gray-value (lighter gray) associated with a pixel, the nearer is it situated to the reference plane. A depth map makes it possible to obtain from the starting image a second image that, together with the starting image, constitutes a stereoscopic pair providing a three-dimensional vision of the scene.
Various techniques are known for creating a depth map. Some of these are described in the publications U.S. Pat. No. 4,947,347, JP 2001155153, U.S. Publication No. 2003/0043270 and WO 02/095680. The known techniques have proved unsatisfactory for various reasons, some because they call for the analysis of various images to obtain the depth information, others because they require the intervention of an operator to identify objects of the image, and yet others because the processing times are very long.